The present invention relates generally to gas transfer systems, and more particularly to a system for filling a receiving cylinder with gaseous fuel.
The increasing demand for alternative fuel vehicles, specifically hydrogen gas fueled vehicles, will require hydrogen fueling stations that can efficiently provide rapid gas filling to vehicles being filled, and efficiently use available gas storage to provide as many fills as possible. One type of gaseous fuel powered vehicle is a fuel cell vehicle (FCV), which uses a fuel cell to electrochemically generate electricity from hydrogen fuel and uses the electricity to power the vehicle. FCVs may use pure hydrogen delivered directly from a hydrogen fueling station.
Hydrogen for use as a fuel in a FCV can be stored in vehicles as a gas in suitable containers, referred to as cylinders. Typically, presently available vehicle cylinders are rated up to 6500 p.s.i. at standard temperature conditions. Obviously, the hydrogen gas cylinder(s) in a vehicle must be recharged from time to time, and it is highly desirable to charge a vehicle""s hydrogen cylinder(s) to the highest pressure possible within a given period of time. A station for dispensing hydrogen gas may store the hydrogen gas in banks of cylinders. These cylinder(s) can initially be all charged to full, but as gas is dispensed the cylinder(s) will be at varying pressures below a complete charge. The process of withdrawing the gas and charging individual station cylinders may result in more or less efficient use of the stored gas, and faster or slower time to fill a vehicle cylinder.
One solution for rapid filling is a charging system by McJones, in U.S. Pat. No. 3,719,196, which describes a system to sequentially charge and discharge from a group of containers, for use in filling vehicle cylinders with natural gas. The use of sequential dispensing assists in effective maximum utilization of the filling force available. The system of ""196 requires a continuous source of pressurized gas, such as a large storage container, from which the series of containers are charged in a sequential process, in preparation for a selective sequence of dispensing. Hence the system and process is not closed, and is not the most efficient for a standalone station which is periodically recharged. There is no internal transfer or charge between the series of containers.
According to one aspect of the invention, there is provided a method of filling a receiving cylinder with gas that includes the following steps: a) flowing a first gas stream from a first dispensing cylinder to a receiving cylinder using a pressure differential between the cylinders; b) when the pressure differential between the first dispensing cylinder and the receiving cylinder has fallen to a selected value, stopping the flow of the first gas stream, then flowing a second gas stream from a second dispensing cylinder to the receiving cylinder using a pressure differential between the second dispensing cylinder and the receiving cylinder; and c) when the pressure differential between the second dispensing cylinder and the receiving cylinder has fallen to a selected value, stopping the flow of the second gas stream, then increasing the pressure of a third gas stream from the first dispensing cylinder to a pressure greater than the pressure in the second dispensing cylinder, and then flowing the third gas stream into the second dispensing cylinder until the pressure in the second cylinder has increased to a selected value.
In this method, the third gas stream pressure may be increased by an intensifier. The intensifier may be powered by one of a hydraulic pump, an air compressor and an electric motor. Or, the intensifier may be powered by a gas stream from one of the dispensing cylinders; in such case, the method includes an additional step before step (a), namely, flowing a fourth gas stream from the first dispensing cylinder, through a driver of the intensifier then to the receiving cylinder using a pressure differential between the first dispensing cylinder and the receiving cylinder, and then flowing the third gas stream from the first dispensing cylinder through a compressor of the intensifier to increase the third gas stream pressure.
In step (b), the first gas stream flow may be stopped when the pressures of the first dispensing cylinder and receiving cylinder have equalized. In step (c), the second gas stream flow is stopped when the pressures of the second dispensing cylinder and receiving cylinder have equalized.
According to another aspect of the invention, there is provided a method of filling a receiving cylinder with gas using an intensifier having a compressor powered by a gas driver; the method includes the following steps: a) flowing a first gas stream from a first dispensing cylinder, through a driver of an intensifier and then to a receiving cylinder using a pressure differential between the cylinders; b) flowing a second gas stream from the first dispensing cylinder through a compressor of the intensifier such that the pressure of the second gas stream is increased above the pressure of a second dispensing cylinder, then flowing the second gas stream to the second dispensing cylinder; c) when the pressure differential between the receiving cylinder and the first dispensing cylinder has fallen to a first selected value, stopping the flow of the first and second gas streams, then flowing a third gas stream from the first dispensing cylinder to the receiving cylinder that bypasses the intensifier and uses a pressure differential between the first dispensing cylinder and the receiving cylinder; and d) when the pressure differential between the receiving cylinder and the first dispensing cylinder has fallen to a second selected value, stopping the flow of the third gas stream, then flowing a fourth gas stream from the second dispensing cylinder to the receiving cylinder using a pressure differential between the second dispensing cylinder and the receiving cylinder.
According to another aspect of the invention, there is provided a gas dispensing system for filling a receiving cylinder with gas. The system includes: a) a receiving cylinder port fluidly connectable to a receiving cylinder; b) a first dispensing cylinder; c) a second dispensing cylinder; d) a gas pressure intensifier; e) a fluid flow circuit comprising fluid conduits fluidly coupling the first dispensing cylinder to the receiving cylinder port, the second dispensing cylinder to the receiving cylinder port, and the first dispensing cylinder to the second dispensing cylinder, and wherein the intensifier is fluidly coupled to the fluid flow circuit such that the pressure of a gas stream from the first cylinder can be increased above the pressure of the second cylinder thereby enabling the gas stream to be flowed from the first cylinder into the second cylinder; and f) gas flow valves fluidly coupled to the fluid flow circuit such that a gas stream can be controlled to flow from the first dispensing cylinder to the receiving cylinder port, from the second dispensing cylinder to the receiving cylinder port, and from the first receiving cylinder through the intensifier and to the second receiving cylinder.
The intensifier may be powered by one of a hydraulic pump, an air compressor and an electric motor. Or, the intensifier may comprise a compressor and a gas driver that powers the compressor, and the fluid flow circuit may further comprise a first fluid flow path from the first dispensing cylinder through the driver and to the receiving cylinder port, and a second fluid flow path from the first dispensing cylinder through the compressor and to the second dispensing cylinder. The gas flow valve may be configured to direct first and second gas streams through the first and second fluid flow paths such that the first gas stream powers the intensifier to increase the pressure of the second gas stream flowing therethrough.